Since launching in 2011, Forgeline’s Concave Series wheels have become incredibly popular.  And we continue to expand our Concave Series with new styles and offerings.  But one point of confusion that we hear frequently is the desire to combine deep reverse rim lips with concave centers – which, depending on wheel width and offset, may not be entirely possible.

In an ideal scenario, some customers understandably want both a concave center AND a really deep rim lip because, well…it looks cool.  However, with some fitment specifications (specifically fitments with narrower overall widths and/or larger offsets), you simply may not have enough room built into the wheel to allow for both a concave profile and a deep reverse lip.

At first glance, you may not understand why this is.  But as you can see from the image below, the concave center spokes literally occupy the space that otherwise belongs to the outer rim.  So holding overall width and backspacing constant, a wheel with a concave center will always have less available outer rim depth than a rim with a non-concave center.

Non-Concave Wheel on the Left, Concave Wheel on the Right

Cross Section View: Non-Concave Wheel on the Left, Concave Wheel on the Right

Both wheels depicted in this image are 11 inch widths with 6.370 inches of backspacing.  They are shown sitting on their backs with the fronts of the wheels facing upward and the backs of the wheels facing downward.  The wheel on the left is a non-concave profile while the wheel on the right is a concave profile.  As you can see, the rim register (mating surface between the center and the rim) on the non-concave wheel on the left is only slightly above the center’s mounting surface at the hub.  In contrast to this, the rim register on the concave wheel on the right reaches way up above the center’s mounting surface at the hub (which is what creates the concave shape) and is occupying the space that would otherwise be available for outer rim lip depth.

Obviously, this may not be an issue for vehicles that can accommodate really small backspacing and really wide widths.  But for most vehicles, there will be some tradeoff between the concave profile and the outer rim lip depth.

For more information about Forgeline’s Concave Series wheels, please visit

July 11, 2012 at 5:14 pm
Category: Tech Talk
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